Pentaceratops

Phylogeny: Dinosauria > Ornithischia > Genasauria > Neornithischia > Cerapoda > Marginocephalia > Ceratopsia > Neoceratopsia > Coronosauria > Ceratopsoidea > Ceratopsidae > Chasmosaurinae

Overview: Pentaceratops, like the famous Triceratops, has a generic name denoting the number of its horns. In its case, rather than three, this was supposedly five. Two of its “horns”, however, were actually its cheek bones. In fairness, said cheek bones were quite elongated and pointed, probably shrouded in life by keratinous coverings like its actual horns, which included a small nasal horn and a pair of rather long brow horns. The brow horns of Pentaceratops would’ve doubled as both display and defensive structures against large tyrannosaurs like Bistahieversor. The frill is reconstructed as elongated and rectangular, fringed by a series of small hornlets. It bore a pair of large openings, in life covered by skin and scales, which rendered the frill fairly fragile and not particularly useful as a shield. The frill may’ve been brightly colored or patterned, used for courtship or to intimidate. Similar to other ceratopsids, Pentaceratops was a heavily built low-browsing herbivore, feeding on ferns, cycads and flowering shrubs.

Fossilized remains definitively belonging to Pentaceratops come from the rocks of New Mexico’s Kirtland and Fruitland formations, as well as the Williams Fork Formation in Colorado. The first of these remains were found in 1921 by fossil hunter Charles H. Sternberg, in New Mexico, made up of a decent portion of the skull. It was described by the renowned Henry F. Osborn in 1923, today on display at the American Museum of Natural History. Numerous other specimens would be found and described over the following years, some possibly representing a second species, though this is thought unlikely by most. Remains of a particularly large individual may belong to Pentaceratops, or alternatively to a separate genus called Titanoceratops, more closely related to Triceratops itself. All three ceratopsids belong to the subfamily Chasmosaurinae. Now distinct taxa like Terminocavus and Bisticeratops were once referred to Pentaceratops.